I have noticed on cold days that there is a loud whining noise in the front end of my 2004 fx4 f-150. When you engage the 4x4 then the noise stops and then when you disengage it on some days it starts up again after you come to a stop and then start going again. It is never a constant but seems to go away after the truck warms up. There is no loose vac lines or leaks and the fluid levels are ok. ANY IDEAS!!!!!!!

 

I have the same problem with my F150 2005. It's only during cold weather and stops when I tap the brake or tap the gas peddle. I asked a mechanic from Ford down near Detroit and he told me it was when moisture got in the 4x4 accelanoid under the hood. My owners manual shows 2 and I haven't been able to figure which one to change. Any other ideas ?